aptdaemon debconf-communicate should be running as root

aptdaemon runs as the session user. It needs to spawn debconf-communicate to interact with the user when packages have debconf questions; which often needs to be done as root (or otherwise have sufficient privileges) since packages may want to prompt for passwords, which use a different, more secure debconf database than the main config one.

aptdaemon probably should be spawning debconf-communicate as root, at the cost of prompting the user for a password when debconf access is necessary.

This became readily apparent with https://bugs.launchpad.net/ubuntu/+source/shim-signed/+bug/1599051; updating to a new shim which requires inputting a Secure Boot password to disable shim validation would consistently fail due to being unable to access password.dat (you would see errors on the command line when update-manager is started in a terminal)